This invention relates to battery plants and to a battery floated across the input to a voltage/battery polarity switch (BPS) or other noisy load, for supplying reserve energy to back up rectified AC energy. It is particularly concerned with blocking current pulses/spikes at the battery terminals, during float charging, due to switching of power switches of the voltage polarity switch.
A backup battery which is floated across the input of a voltage/battery polarity switch, such as shown in FIG. 1, is subject to large pulses or spikes of current during switching transitions of power switches of the voltage/battery polarity switch (BPS). This is because the load is disconnected and reconnected during each polarity transition, by the rectifying diodes of the load connecting the polarity switches to the load, being back biased during the transitions. These current spikes occur during float charging of the battery and can degrade battery performance and reduce battery life span. In fact any noisy load producing current spikes may have a deleterious effect on the battery.
In one prior art embodiment, having a battery floating across the power rails, as shown in FIG. 2, a capacitor is connected in parallel with the battery terminals in combination with a choke inductance included in one of the rails of the main power path train.
Transient current pulses/spikes generated by switching components of a battery plant are restricted from application to a floating battery, by blocking circuitry which is connected to the battery terminals but mostly located outside of the main power path train, coupling primary power to the switching circuit. This blocks transient current pulses/spikes which may over charge the battery during the float charging operation and damage the battery.
In one exemplary embodiment a saturable choke is connected in series with the battery terminals but outside of the the power flow path/rails from the input rectifier to the voltage polarity switch input. Its electrical characteristics are selected to block the current pulses/spikes generated when the battery is floating and hence is vulnerable to long term degradation due to the overcharge created by current spikes.